A compression encoding technology is used to efficiently transmit and store moving picture data. The MPEG-1 to 4 and ITU (International Telecommunication Union) H.261 to H.264 systems are widely used for moving pictures. In moving picture encoding, a prediction signal of a target picture that is an encoding target is generated by using temporally adjacent pictures and then a residual between the target picture and the prediction signal is encoded, thereby realizing a data amount reduction. This technique is called inter-frame prediction encoding.
For example, in H.264, one frame picture is divided into a plurality of regions of blocks each composed of 16×16 pixels, and encoding processing is performed on the picture on a block-by-block basis. In inter-frame prediction encoding, a prediction signal is generated by performing motion prediction on a certain target block of a target picture using a plurality of other frame pictures that have been encoded and reconstructed (hereinafter, referred to as “reconstructed pictures”) as reference pictures. At this time, the prediction signal is generated by performing block matching on prediction signal candidates with ¼ pixel accuracy generated by performing similar fixed pixel interpolation filtering on a plurality of reference pictures, and selecting a prediction signal candidate having a lowest sum of a code amount when an error with respect to a target block is encoded, and a code amount when an identifier of a reference picture and a displacement (motion vector) from the target block are encoded. Then, discrete-cosine-transformation and quantization processing are performed on a residual signal between the target block and the generated prediction signal, whereby encoded data is generated.